doc/man/man3/dlsym.3

   1 .Dd Sept 25, 2004
   2 .Dt DLSYM 3
   3 .Sh NAME
   4 .Nm dlsym
   5 .Nd get address of a symbol
   6 .Sh SYNOPSIS
   7 .In dlfcn.h
   8 .Ft void*
   9 .Fn dlsym "void* handle" "const char* symbol"
  10 .Sh DESCRIPTION
  11 .Fn dlsym
  12 returns the address of the code or data location
  13 specified by the null-terminated character string
  14 .Fa symbol .
  15 Which libraries and bundles are searched depends on the
  16 .Fa handle
  17 parameter.
  18 .Pp
  19 If
  20 .Fn dlsym
  21 is called with a
  22 .Fa handle ,
  23 returned by
  24 .Fn dlopen
  25 then only that image and any libraries it depends on are searched for
  26 .Fa symbol .
  27 .Pp
  28 If
  29 .Fn dlsym
  30 is called with the special
  31 .Fa handle
  32 .Dv RTLD_DEFAULT ,
  33 then all mach-o images in the process (except those loaded with dlopen(xxx, RTLD_LOCAL))
  34 are searched in the order they were loaded.
  35 This can be a costly search and should be avoided.
  36 .Pp
  37 If
  38 .Fn dlsym
  39 is called with the special
  40 .Fa handle
  41 .Dv RTLD_NEXT ,
  42 then the search for the symbol is limited to the images which were loaded
  43 after the one issuing the call to
  44 .Fn dlsym .
  45 .Pp
  46 .Sh RETURN VALUES
  47 The
  48 .Fn dlsym
  49 function
  50 returns a null pointer if the symbol cannot be found, and sets an error
  51 condition which may be queried with
  52 .Fn dlerror .
  53 .Pp
  54 .Sh NOTES
  55 Unlike other dyld API's, the symbol name passed to
  56 .Fn dlsym
  57 must NOT be prepended with an underscore.
  58 .Sh SEE ALSO
  59 .Xr dlopen 3
  60 .Xr dlsym 3
  61 .Xr dlerror 3
  62 .Xr dyld 3
  63 .Xr NSModule 3
  64 .Xr NSObjectFileImage 3
  65 .Xr ld 1
  66 .Xr cc 1